Abstract

The principal object of this work is to determine how to adjust a Compton electrometer for maximum charge sensitivity. First some disputed points in the theory of the charge sensitivity are treated and the solutions obtained here are confirmed experimentally. With the aid of direct measurements of the fundamental dimensions of the electrometer, its capacity, and the torsion constant of its suspension, actual values are calculated for the constants usually left arbitrary in the theoretical expressions for charge and voltage sensitivity. The resulting sensitivity formulas are confirmed experimentally. The theoretical expression for charge sensitivity is examined in order to determine the conditions for highest charge sensitivity subject to the restriction that the time required for a deflection to reduce to e−1 of its maximum value after the quadrants are grounded be not greater than some arbitrary time T0. The maximum value of the charge sensitivity thus obtained is (T0/βC)½/2 where β≅damping torque of needle per unit of angular velocity, and C=capacity of whole collecting system of electrometer to surroundings.